Caribbean - Central America Weather

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
502 AM AST MON MAY 11 2015

.SYNOPSIS...BROAD MID TO UPPER LEVEL HIGH PRESSURE RIDGE ACROSS
THE EASTERN CARIBBEAN EXTENDS NORTHWARDS ACROSS THE EASTERN
CARIBBEAN....WHILE A HIGH AMPLITUDE UPPER TROUGH EXTENDS
SOUTHWARDS ACROSS THE SOUTHWEST ATLANTIC THEN INTO THE EAST
CENTRAL CARIBBEAN. THIS WILL MAINTAIN A DOMINANT SOUTHWEST WIND
FLOW ACROSS THE REGION OVER THE NEXT FEW DAYS. THE UPPER TROUGH IS
HOWEVER FORECAST TO WEAKEN BY THE LATTER PART OF THE WEEK AS IT
WILL GRADUALLY LIFT NORTHEASTWARD AND FILL. IN THE MEANTIME THIS
FEATURE WILL HELP TRANSPORT MID TO UPPER CLOUDINESS ACROSS THE
FORECAST AREA OVER THE NEXT FEW DAYS...AS WELL AS PROVIDE UPPER
LEVEL INSTABILITY. BROAD AND STRONG SURFACE HIGH PRESSURE RIDGE
NORTH OF THE REGION WILL MAINTAIN A FAIRLY TIGHT PRESSURE GRADIENT
ACROSS THE NORTHEASTERN CARIBBEAN. THIS WILL CREATE MODERATE TO
STRONG EASTERLY TRADE WIND THROUGH THE EARLY PART OF THE WORK
WEEK. LATEST SATELLITE IMAGERY SHOWED A WEAKLY INDUCED LOW LEVEL
TROUGH AND ACCOMPANYING AREA OF LOW LEVEL MOISTURE MOVING ACROSS
THE LESSER ANTILLES AND ENTERING THE EASTERN CARIBBEAN.

&&

.DISCUSSION...THE DOMINANT EASTERLY TRADES WILL CONTINUE TO
TRANSPORT WEAK EASTERLY PERTUBATIONS AND OCCASIONAL PATCHES OF
MOISTURE ACROSS THE REGION DURING THE NEXT FEW DAYS. THE
PROXIMITY OF THE UPPER LEVEL TROUGH AND THE ANTICYCLONIC FLOW
ACROSS THE NORTHEASTERN CARIBBEAN...WILL PROVIDE SUFFICIENT
INSTABILITY ACROSS THE ISLANDS AND COASTAL WATERS. THIS WILL
SUPPORT PERIODS OF ISOLATED TO SCATTERED CONVECTION ACROSS THE
REGION AT LEAST THROUGH WEDNESDAY AND POSSIBLE ON THURSDAY. EXPECT
THE MAIN ACTIVITY TO BE HOWEVER FOCUSED OVER PARTS OF THE WEST AND
NORTHWEST SECTION OF PUERTO RICO DURING THE DAYTIME WHERE
THUNDERSTORM DEVELOPMENT WILL REMAIN POSSIBLE EACH AFTERNOON. SOME
ENHANCED CONVECTION CAN ALSO BE EXPECTED ACROSS PARTS OF THE
COASTAL WATERS ESPECIALLY DURING THE LATE EVENINGS AND EARLY
MORNING HOURS. SOME SHOWERS MAY REACH PARTS OF THE EAST COASTAL
SECTION OF THE ISLANDS FROM TIME TO TIME. THIS PATTERN WILL
CONTINUE UNTIL MID WEEK...FOLLOWED BY A GRADUAL DECREASE IN
CLOUDINESS AND MOISTURE TRANSPORT AS THE UPPER TROUGH
WEAKENS...AND THE SURFACE ATLANTIC HIGH LIFTS FURTHER NORTH AND
EAST OF THE REGION RESULTING IN A LOOSENING OF THE LOCAL PRESSURE
GRADIENT.

&&

.AVIATION....A LAYER OF MID-UPPER CLOUDS DECK ASSOCIATED WITH A
SOUTHWESTERLY UPPER LEVEL JET WILL MAINTAIN BKN-OVC CIGS BETWEEN
20- 30KFT. THIS CLOUD DECK EXPECTED TO CONTINUE ACROSS THE LOCAL
FLYING AREA DURG THE NXT 24 HOURS. ISOLD-SCT PASSING SHRA EXPECTED
ACROSS PARTS OF TAF SITES XCPT TJPS...TJBQ AND TJMZ. AFTER 05/18Z
ISOLATED TSRA MAY BE POSSIBLE AT TJBQ. EAST WINDS AT 15 TO 20 KNOTS
WITH BRIEF GUSTS BETWEEN 25 AND 30 KT WILL REMAIN POSSIBLE BETWEEN
11/14Z-11/22Z.

&&

.MARINE...THE STRONG HIGH PRESSURE RIDGE NORTH OF THE REGION WILL
MAINTAIN A TIGHT PRESSURE GRADIENT ACROSS THE REGIONAL WATERS. THIS
WILL RESULT IN MODERATE TO FRESH TRADE WINDS WITH WIND DRIVEN SEAS
OF UP TO 7 FEET IN SOME OF THE OFFSHORE WATERS AND LOCAL PASSAGES.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 90 77 / 20 30 30 20
STT 88 79 87 77 / 10 30 30 30

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
318 PM AST MON MAY 11 2015

.SYNOPSIS...AS AN UPPER LEVEL TROUGH REACHES THE LOCAL AREA THE
RIDGE ALOFT WILL CONTINUE TO ERODE. SURFACE HIGH PRESSURE WILL
CONTINUE TO TIGHTEN THE LOCAL PRESSURE GRADIENT. THIS WILL RESULT
IN MODERATE TO FRESH TRADE WINDS. A MID TO UPPER LEVEL CLOUD DECK
WILL CONTINUE DURING THE NEXT DAYS.

.DISCUSSION...

SHORT TERM...UPPER LEVEL RIDGE WILL CONTINUE TO ERODE AS THE
UPPER LEVEL TROUGH MOVES ACROSS WESTERN ATLANTIC...PRODUCING
ENOUGH INSTABILITY TO GENERATE PASSING SHOWERS FROM TIME TO TIME
ACROSS THE CWA. ALSO...ANOTHER SURFACE DISTURBANCE AND A SLIGHT
INCREASE IN SURFACE MOISTURE IS EXPECTED TODAY AND TONIGHT ACROSS
THE LOCAL ISLANDS. DURING THE NIGHT TIME...PASSING SHOWERS MAY
AFFECTED THE EASTERN SECTIONS OF PR AND THE USVI AS WELL AS THE
LOCAL WATERS. IN ADDITION...A MID TO UPPER LAYER OF HIGH CLOUDS
HAVE BEEN OBSERVED ACROSS PR AND USVI...AND WILL PERSIST AT LEAST
UNTIL MID WEEK.

LONG TERM...SHOWER ACTIVITY IS EXPECTED TO INCREASE AS THE UPPER
LEVEL TROUGH REACHES THE LOCAL AREA...WEDNESDAY LOOKS LIKE THE
BEST DAY FOR SHOWER AND T-STORM ACTIVITY MAINLY ACROSS THE
INTERIOR AND WESTERN SECTIONS OF PUERTO RICO...AND DOWNWIND FROM
THE VIRGIN ISLANDS. MEANWHILE...AEROSOL MODELS AND SATELLITE
IMAGES SUGGEST THE ARRIVAL OF A SAHARAN AIR LAYER ACROSS THE
CWA...BY LATE TUESDAY...WITH THE HIGHER CONCENTRATIONS ON
WEDNESDAY. AFTER WEDNESDAY...TRANQUIL WX CONDITIONS ARE EXPECTED
ACROSS THE LOCAL ISLANDS.

&&

.AVIATION...MOSTLY VFR CONDS AT ALL TAF SITES WITH BRIEF MVFR
CONDS POSSIBLE IN AND AROUND JSJ THIS AFTERNOON. PERIODS OF MVFR
CONDS EXPECTED AT JMZ AND JBQ THROUGH 11/23Z IN SHRA AND TSRA. EAST
SOUTHEAST WINDS 15 TO 20 KNOTS WITH BRIEF GUSTS BETWEEN 25 AND 30
KT...BECOMING AROUND 10 KNOTS OVERNIGHT.

&&

.MARINE...MODERATE TO FRESH EAST WINDS BETWEEN 15 AND 20 KTS AND
GUSTS UP TO 25 KT HAVE BEEN OBSERVED BY THE LOCAL BUOY NETWORK.
CHOPPY SEAS BETWEEN 3 AND 6 FEET ARE EXPECTED ACROSS THE LOCAL
WATERS. ON THE OTHER HAND...SEAS UP TO 7 FEET ARE EXPECTED DUE TO
WINDY CONDITIONS ACROSS THE OFFSHORE WATERS AND LOCAL PASSAGES.
THEREFORE...THE NWS HAS ISSUED AN SMALL CRAFT ADVISORY FOR THE
AFOREMENTIONED LOCALE...ELSEWHERE...MARINERS SHOULD EXERCISE
CAUTION.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 89 78 89 / 30 30 20 30
STT 79 87 79 87 / 30 30 30 30

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
454 AM AST TUE MAY 12 2015

.SYNOPSIS...UPPER TROUGH JUST WEST OF THE REGION EXTENDS FROM THE
SOUTHWEST ATLANTIC SOUTHWARD ACROSS JAMAICA INTO THE CENTRAL CARIBBEAN.
MEANWHILE SLOWLY ERODING UPPER LEVEL RIDGE EXTENDS NORTHWARDS ACROSS
THE REGION FROM THE EASTERN CARIBBEAN. THIS PATTERN WILL MAINTAIN
THE SOUTHWEST UPPER LEVEL WIND FLOW WHICH IN TURN CONTINUE TO TRANSPORT
WIDESPREAD HIGH LEVEL CLOUDINESS ACROSS THE ISLANDS AND COASTAL WATERS.
THE UPPER TROUGH IS TO SLOWLY FILL/WEAKEN AND LIFT EAST NORTHEAST ACROSS
THE REGION BY THURSDAY. UPPER HIGH WILL THEN REESTABLISH ACROSS THE
AREA ON FRIDAY. STRONG SURFACE HIGH PRESSURE RIDGE NORTH OF THE REGION
SPREAD ACROSS THE ATLANTIC...WILL MAINTAIN A FAIRLY TIGHT PRESSURE
GRADIENT AND MODERATE TO STRONG EASTERLY TRADES ACROSS THE FORECAST
AREA AT LEAST UNTIL THURSDAY. THEREAFTER THE RIDGE IS TO GRADUALLY
LOOSEN ITS HOLD AND ALLOW FOR DIMINISHING TRADE WINDS BY FRIDAY
AND INTO THE UPCOMING WEEKEND. SATELLITE IMAGERY SHOWED CONSIDERABLE
AMOUNTS OF HIGH LEVEL CLOUDS SPREAD ACROSS THE REGION...WITH
SHALLOW LOW LEVEL CLOUDS AND A FEW LIGHT SHOWERS MOVING WESTWARDS
ACROSS THE FORECAST AREAS IN THE DOMINANT EASTERLY TRADES.

&&

.DISCUSSION...
EXPECT MINIMAL CONVECTIVE ACTIVITY ACROSS THE REGION TODAY AS THE PRESENCE
OF WIDESPREAD HIGH LEVEL CLOUDS SHOULD HELP LIMIT ANY SIGNIFICANT
CONVECTIVE DEVELOPMENT ACROSS THE ISLANDS. A FEW SHOWERS MAY HOWEVER
DEVELOP LATE IN THE AFTERNOON MAINLY ACROSS PORTIONS OF THE WEST INTERIOR
SECTIONS OF PUERTO RICO BUT DO NOT EXPECT SIGNIFICANT AMOUNTS OF RAINFALL
AT THIS TIME. ELSEWHERE MOSTLY SUNNY AND AND OVERALL HAZY CONDITIONS
WILL PERSIST AS FINE AMOUNTS OF SUSPENDED SAHARAN DUST PARTICULATES
WILL CONTINUE TO SPREAD WESTWARDS ACROSS THE REGION.

BY EARLY WEDNESDAY EXPECT HIGH LEVEL CLOUDINESS TO DIMINISH AS
TROUGH AXIS ALOFT LIFT NORTHWARDS. THIS WILL ALLOW BETTER DAYTIME
HEATING AND INCREASE THE CHANCE FOR DIURNALLY INDUCED AFTERNOON
CONVECTION ACROSS THE ISLANDS ESPECIALLY ACROSS THE WEST INTERIOR
SECTION OF PUERTO RICO...WHERE LOCAL SEA BREEZE CONVERGENCE AND
FORCING WILL BE STRONGER. ENHANCED AFTERNOON CONVECTION WILL ALSO
BE POSSIBLE ON THURSDAY ESPECIALLY IN THE WEST AND SOUTHWEST
SECTIONS OF PUERTO RICO...WHEN UPPER LEVEL INSTABILITY AND GOOD
VENTILATION WILL SUPPORT THUNDERSTORM DEVELOPMENT. A GRADUALLY
IMPROVEMENT IS SO FAR FORECAST FOR FRIDAY AND INTO THE UPCOMING
WEEKEND AS THE EASTERLY TRADE WINDS DIMINISH...UPPER LEVEL RIDGE
BUILDS ACROSS THE REGION ONCE AGAIN...AND TRADE WIND MOISTURE
ADVECTION DECREASES.

&&

.AVIATION...MOSTLY VFR CONDITIONS EXPECTED ACROSS THE LOCAL
FLYING AREA NEXT 24 HOURS WITH ONLY ISOLATED SHRA UNTIL 12/14Z OVER
LOCAL WATERS AND EASTERN PR WITH MOUNTAIN OBSCURATIONS...THEN AFTER
12/16Z...ISOLATED SHRA ACROSS WESTERN PR WILL PRODUCE BRIEF PERIODS
OF MVFR CONDITIONS POSSIBLE BETWEEN TJMZ AND TJBQ. WINDS ESE AT 10
KT UNTIL 12/14Z THEN INCREASING TO EAST SOUTHEAST WITH SEA BREEZE
VARIATIONS AT 15 TO 20 KNOTS WITH BRIEF GUSTS TO BETWEEN 25 AND 30
KT. HEAVY CI LAYER AT AND ABOVE FL230.

&&

.MARINE...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE OFFSHORE
ATLANTIC AND CARIBBEAN WATERS AS WELL AS THE MONA PASSAGE. LATEST
MODEL GUIDANCE AND RECENT BUOY DATA HAVE CONTINUED TO ALIGN PRETTY
WELL AND SUGGEST WINDS UP TO 21 KNOTS...AND CHOPPY SEA CONDITIONS
UP TO 7 FEET ACROSS THE LOCAL OFFSHORE WATERS AND THE MONA PASSAGE.
PLEASE REFER TO THE LATEST COASTAL WATERS FORECAST AND THE MARINE
WEATHER MESSAGE ISSUED BY WFO SAN JUAN PR FOR ADDITION INFO AND
UPDATES. EASTERLY TRADE WINDS ARE TO RELAX ACROSS THE REGION BY
THURSDAY AND FRIDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 88 77 / 20 20 30 40
STT 88 78 87 77 / 20 30 30 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
343 PM AST TUE MAY 12 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH CURRENTLY ACROSS THE WESTERN
CARIBBEAN WILL CONTINUE TO APPROACH THE LOCAL AREA...INCREASING
THE LOCAL INSTABILITY. BY THE END OF THE WORKWEEK...AS THE UPPER
LEVEL TROUGH LEAVES THE AREA A MID-UPPER LEVEL RIDGE WILL BUILD
OVER THE AREA. SURFACE HIGH PRESSURE JUST NORTH OF THE ISLANDS
WILL CONTINUE TO TIGHTEN THE LOCAL PRESSURE GRADIENT RESULTING
IN MODERATE TO FRESH TRADE WINDS. AN UPPER LEVEL JET SEGMENT WILL
CONTINUE TO BRING MID-HIGH LEVEL CLOUDINESS.

&&

.DISCUSSION...
HAZY SKIES AND WINDY CONDITIONS CONTINUE ACROSS THE LOCAL AREA
TODAY. ALSO...AN UPPER LEVEL JET CONTINUE TO BRING MID-UPPER
LEVEL CLOUDINESS ACROSS THE LOCAL SKIES. AS THE LOCAL SKIES
CLEARED...SHOWERS AND T-STORMS DEVELOPED ACROSS THE WESTERN
SECTIONS OF PUERTO RICO DURING THE AFTERNOON HOURS. SHOWERS AND
ISOLATED T-STORMS ARE EXPECTED TO CONTINUE UNTIL THE EVENING
HOURS. FOLLOWED BY SOME PASSING SHOWERS ACROSS THE WINDWARD
SECTIONS OF PR AND THE USVI OVERNIGHT.

BY WEDNESDAY AFTERNOON...AN UPPER LEVEL TROUGH WILL CREATE ENOUGH
UPPER LEVEL DIFFLUENCE. IN ADDITION...MODEL GUIDANCE SUGGESTS
INCREASING K-INDEX...AND MID-UPPER LEVEL INSTABILITY...
THEREFORE SHOWER AND T-STORM ACTIVITY IS EXPECTED ACROSS THE LOCAL
ISLANDS AND SURROUNDING WATERS. THE UPPER LEVEL TROUGH PATTERN
WILL CONTINUE TO PREVAIL THROUGH EARLY THURSDAY.

A MID TO UPPER LEVEL RIDGE WILL THEN BUILD FROM THE WEST AS
THE TROUGH AXIS MOVES AWAY WITH FAIR AND STABLE WEATHER EXPECTED
BY THE END OF THE WORKWEEK AND THE UPCOMING WEEKEND.

&&

.AVIATION...MOSTLY VFR CONDS AT ALL TAF SITES WITH BRIEF MVFR
CONDS POSSIBLE IN AND AROUND JSJ/JMZ AND JBQ THRU 12/22Z. EAST
SOUTHEAST WINDS 15 TO 20 KNOTS WITH BRIEF GUSTS BETWEEN 25 AND
30 KT...BECOMING NEAR 10 KNOTS OVERNIGHT.

&&

.MARINE...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE OFFSHORE
WATERS AND LOCAL PASSAGES...DUE TO CHOPPY SEAS UP TO 7 FEET AND
WINDS AROUND 20 KNOTS. ELSEWHERE...SMALL CRAFT OPERATORS SHOULD
EXERCISE CAUTION.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 89 77 89 / 20 30 40 30
STT 78 88 77 88 / 30 30 40 30

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
446 AM AST WED MAY 13 2015

.SYNOPSIS...UPPER TROUGH JUST WEST OF THE REGION EXTENDS FROM
THE WESTERN CARIBBEAN NORTHWARD ACROSS CUBA AND BAHAMAS INTO THE
SOUTHWEST ATLANTIC...WILL CONTINUE TO APPROACH THE LOCAL AREA
WHILE WEAKENING. THIS FEATURE WILL ERODE THE UPPER LEVEL RIDGE
ACROSS THE REGION...SLIGHTLY INCREASING THE LOCAL INSTABILITY
WHICH MAY HELP WITH THE DEVELOPMENT OF SHOWERS AND ISOLATED
THUNDERSTORMS THIS AFTERNOON AND TOMORROW AFTERNOON. AS THE UPPER
LEVEL TROUGH LEAVES THE AREA A MID-UPPER LEVEL RIDGE WILL BUILD
AGAIN OVER THE AREA. SURFACE HIGH PRESSURE JUST NORTH OF THE
ISLANDS WILL CONTINUE TO TIGHTEN THE LOCAL PRESSURE GRADIENT
RESULTING IN MODERATE TO FRESH TRADE WINDS. AN UPPER LEVEL JET
SEGMENT WILL CONTINUE TO BRING MID-HIGH LEVEL CLOUDINESS.

&&

.DISCUSSION...DOPPLER WEATHER RADAR DETECTED ONLY ISOLATED SHOWERS
OVER EASTERN PUERTO RICO AND ACROSS THE CARIBBEAN WATERS OVERNIGHT
AND EARLY THIS MORNING. ELSEWHERE OVER THE REGION NOT SIGNIFICANT
PRECIPITATION WAS DETECTED. FOR THIS AFTERNOON...AN UPPER LEVEL
TROUGH WILL CREATE ENOUGH UPPER LEVEL DIFFLUENCE ACROSS THE
FORECAST AREA. IN ADDITION...MODEL GUIDANCE SUGGESTS INCREASING
K-INDEX...AND MID-UPPER LEVEL INSTABILITY AS THE UPPER RIDGE ERODE
RAPIDLY. NAAPS AEROSOL MODEL INDICATES THAT THE DUST CONCENTRATION
WILL DECREASE SIGNIFICANTLY TODAY AND INTO THE NEXT FEW DAYS. SO
THE SAHARAN DUST MAY NOT BE PRESENT TO LIMIT CONVECTION THIS
AFTERNOON...BUT MID LAYERS STILL LOOK A BIT ON THE DRY SIDE.
LATEST OBSERVATIONS AND GUIDANCE SUGGESTS THAT THE HIGH LEVEL
CLOUDINESS WILL DIMINISH AS TROUGH AXIS ALOFT LIFT NORTHWARDS.
THIS WILL ALLOW BETTER DAYTIME HEATING AND INCREASE THE CHANCE FOR
DIURNALLY INDUCED AFTERNOON CONVECTION ACROSS THE ISLANDS
ESPECIALLY ACROSS THE WEST INTERIOR SECTION OF PUERTO RICO...WHERE
LOCAL SEA BREEZE CONVERGENCE AND FORCING WILL BE STRONGER. SO
SCATTERED SHOWERS WITH A FEW THUNDERSTORMS ACROSS WESTERN PR WERE
KEPT IN THE FORECAST FOR THIS AFTERNOON WITH ISOLATED SHOWERS
ELSEWHERE...AS THE UPPER LEVEL TROUGH PATTERN CONTINUES TO PREVAIL
ACROSS THE REGION. ENHANCED AFTERNOON CONVECTION WILL ALSO BE POSSIBLE
ON THURSDAY ESPECIALLY IN THE WEST AND CENTRAL SECTIONS OF PUERTO
RICO...WHEN UPPER LEVEL INSTABILITY AND GOOD VENTILATION WILL
SUPPORT THUNDERSTORM DEVELOPMENT. HOWEVER THESE ARE NOT EXPECTED
TO BE LONG LASTING BECAUSE A MID TO UPPER LEVEL RIDGE WILL BUILD
FROM THE WEST AS THE UPPER TROUGH AXIS MOVES AWAY WITH A RETURN TO
A MOSTLY FAIR AND STABLE WEATHER EXPECTED BY THE END OF THE
WORKWEEK AND DURING THE UPCOMING WEEKEND.

&&

.AVIATION...MOSTLY VFR CONDS AT ALL TAF SITES WITH BRIEF MVFR CONDS
POSSIBLE IN AND AROUND TJMZ AND TJBQ AFT 13/17Z. ALSO ISOLD TSRA WRN
PR ALONG WITH AREAS OF MTN OBSCURATIONS. WINDS ESE 10 TO 15 KNOTS
OVERNIGHT THEN AFT 13/14Z EAST SOUTHEAST WINDS 15 TO 20 KNOTS WITH
GUSTS BETWEEN 23 AND 28 KT. HEAVY CI CLDS ABOVE FL220.

&&

.MARINE...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR MARINE ZONES
710...732 AND 741 DUE TO SEAS UP TO 7 FEET AND WINDS UP TO 20
KNOTS. SMALL CRAFT ARE URGED TO EXERCISE CAUTION ACROSS THE REST
OF THE REGIONAL WATERS DUE TO WINDS OF 20 KNOTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 89 77 / 20 40 30 20
STT 87 77 88 77 / 30 40 30 30

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
327 PM AST WED MAY 13 2015

.SYNOPSIS...MID TO UPPER LEVEL RIDGE WILL BUILD FROM THE WEST AS
TROUGH ALOFT MOVES EASTWARD WHILE ERODES. THE MID TO UPPER LEVEL
RIDGE WILL THEN HOLD THROUGH EARLY NEXT WEEK. LOCAL PRESSURE
GRADIENT WILL RELAX OVER THE NEXT FEW DAYS AS BROAD SURFACE
HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC SHIFTS EASTWARD.

&&

.DISCUSSION...MOSTLY SUNNY SKIES PREVAILED ACROSS THE LOCAL ISLANDS
TODAY...WITH BRIEF PASSING SHOWERS NOTED OVER EASTERN PR AND THE
ATLANTIC WATERS EARLY THIS MORNING. THUNDERSTORMS WERE ALSO OBSERVED
EARLY THIS AFTERNOON OVER WEST PUERTO RICO. WINDS WERE MAINLY EAST
AT 15 TO 20 MPH WITH COASTAL TEMPERATURES IN THE UPPER 80S AND LOW
90S.

THE PROXIMITY OF AN UPPER LEVEL TROUGH AND BRISK TRADE WINDS WILL
CONTINUE TO RESULT IN BRIEF PASSING SHOWERS ACROSS EASTERN PUERTO
RICO TONIGHT AND THURSDAY MORNING...FOLLOWED BY AFTERNOON SHOWERS
AND A FEW THUNDERSTORMS OVER WESTERN AND NORTHWESTERN PUERTO RICO
THURSDAY AFTERNOON. AS A MID TO UPPER LEVEL RIDGE BUILDS FROM THE
WEST FRIDAY AND INTO THE UPCOMING WEEKEND...A DRIER AND STABLE
AIR MASS WILL PREVAIL ACROSS THE LOCAL ISLANDS. THEREFORE FRIDAY
THROUGH EARLY NEXT WEEK...PARTLY CLOUDY SKIES AND LIMITED SHOWER
ACTIVITY EXPECTED EACH DAY WITH POSSIBLE SHOWER ACTIVITY FOCUSED
OVER THE WESTERN INTERIOR. RIDGE ALOFT WILL HOLD THROUGH EARLY
NEXT WEEK...BUT FLATTENING BY MID WEEK. THIS WILL RESULT IN
BETTER MOISTURE ADVECTION WEDNESDAY THROUGH FRIDAY.

&&

.AVIATION...VFR CONDS WILL PREVAIL AT ALL THE TERMINALS THROUGH
THE FORECAST PERIOD. EAST WINDS OF 15-30 KT CAN BE EXPECTED BELOW
FL050.

&&

.MARINE...SEAS WILL CONTINUE TO DIMINISH OVERNIGHT. SMALL CRAFT
HOWEVER WILL REMAIN IN EFFECT ACROSS THE ATLC OFFSHORE WATERS
TONIGHT. SEAS UP TO 7 FEET AND WINDS AROUND 20 KNOTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 90 77 90 / 20 20 20 20
STT 77 87 76 87 / 20 20 20 20

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
426 AM AST THU MAY 14 2015

.SYNOPSIS...UPPER TROUGH JUST WEST AND NORTH OF THE REGION...
WILL MOVE NORTHWARD WHILE WEAKENING. AS THE UPPER LEVEL TROUGH
LEAVES THE AREA A MID-UPPER LEVEL RIDGE WILL BUILD AGAIN OVER THE
REGION. SURFACE HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC WILL
SHIFT EASTWARD...RELAXING THE LOCAL PRESSURE GRADIENT.

&&

.DISCUSSION...DOPPLER WEATHER RADAR DETECTED ONLY ISOLATED SHOWERS
OVER THE CARIBBEAN WATERS OVERNIGHT AND EARLY THIS MORNING. NOT
PRECIPITATION WAS DETECTED OVER LAND AREAS OVERNIGHT AND EARLY
THIS MORNING. AN UPPER LEVEL TROUGH WEST AND NORTH OF THE REGION
IS EXPECTED TO MOVE NORTHWARD AND EASTWARD WHILE WEAKENING TODAY
AND TOMORROW. NAAPS AEROSOL MODEL INDICATES THAT THE DUST
CONCENTRATION WILL CONTINUE TO DECREASE TODAY AND INTO THE NEXT
FEW DAYS. THIS WILL INCREASE THE CHANCE FOR DIURNALLY INDUCED
AFTERNOON CONVECTION ACROSS THE ISLANDS ESPECIALLY ACROSS THE WEST
AND INTERIOR SECTION OF PUERTO RICO...WHERE LOCAL SEA BREEZE
CONVERGENCE AND FORCING WILL BE STRONGER. SO SCATTERED SHOWERS
WITH A FEW THUNDERSTORMS ARE EXPECTED THIS AFTERNOON ACROSS
THE INTERIOR INTO SOUTHWESTERN PUERTO RICO...WITH ONLY ISOLATED
SHOWERS ELSEWHERE. HOWEVER THESE ARE NOT EXPECTED TO BE LONG
LASTING BECAUSE A MID TO UPPER LEVEL RIDGE IS EXPECTED TO BUILD
FROM THE WEST DURING THE UPCOMING WEEKEND WITH A RETURN TO A
MOSTLY FAIR AND STABLE WEATHER PATTERN EXPECTED BY THE END OF THE
WORKWEEK AND DURING THE UPCOMING WEEKEND. LATEST MODEL GUIDANCE
SUGGESTS THAT BY MID WEEK NEXT WEEK...A LOW PRESSURE CENTER WILL
DEVELOP SOUTH OF JAMAICA. THIS FEATURE IS EXPECTED TO PRODUCE
A LARGE AREA OF MOISTURE WITH PWAT VALUES OVER 2.0 INCHES ACROSS
HISPANIOLA...JAMAICA...CUBA AND PUERTO RICO WEDNESDAY THRU FRIDAY.
STAY TUNED.

&&

.AVIATION...VFR CONDS WILL PREVAIL ACROSS ALL TERMINALS THRU THE
FCST PERIOD. HOWEVER TIL 14/12Z...SCT CLD LYRS BTW FL020-FL050 WITH
FEW TRADE WIND -SHRA EN ROUTE BTW ERN PR AND NRN LEEWARDS. BRIEF
MVFR CONDS PSBL BTW 14/18-21Z AS SHRA /ISOLD TSRA DEVELOP ACROSS THE
WEST AND SOUTHWESTERN INTERIOR PR...AND AFFECT MAINLY TJPS AND TJMZ.
E TO NE WINDS AT 5-15 KTS TIL 14/14Z...LGT/VRB AT SFC. AFT 14/14Z
WND BLO FL150 FM NE 15-20 KTS...SFC WND FM E-NE 10-15 KTS WITH OCNL
HIGHER GUSTS IN THE MID 20S. WND FM W ABV FL150 INCR/W HGT...WIND
MAX AROUND 50 KT BTW FL300-FL350. NO SIG OPERATIONAL WX IMPACTS ATTM.

&&

.MARINE...SEAS WILL CONTINUE TO DIMINISH TODAY. SMALL CRAFT
ARE URGED TO EXERCISE CAUTION ACROSS MOST OF THE LOCAL WATERS DUE
TO SEAS UP TO 6 FEET AND WINDS AROUND 20 KNOTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 87 77 / 20 20 20 30
STT 87 76 87 77 / 20 20 20 30

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
329 PM AST THU MAY 14 2015

.SYNOPSIS...RIDGE ALOFT WILL BUILD FROM THE WEST TONIGHT AND
SATURDAY. HOWEVER THIS FEATURE WILL FLATTEN EARLY NEXT WEEK AS
A BROAD TROUGH DEVELOPS ACROSS THE CENTRAL ATLANTIC. TRADE WINDS
WILL GRADUALLY DIMINISH ACROSS THE LOCAL AREA THROUGH FRIDAY...AS
A BROAD SURFACE HIGH PRESSURE ACROSS THE CENTRAL ATLANTIC SHIFTS
EASTWARD. ANOTHER SURFACE HIGH PRESSURE WILL THEN BUILD ACROSS
THE WESTERN ATLANTIC DURING THE WEEKEND.

&&

.DISCUSSION...MOSTLY SUNNY SKIES PREVAILED ACROSS THE LOCAL ISLANDS
TODAY...WITH SHOWERS AND THUNDERSTORMS OBSERVED OVER PORTIONS OF THE
CORDILLERA CENTRAL AND WEST PUERTO RICO. WINDS WERE MAINLY EAST AT
15 TO 20 MPH WITH COASTAL TEMPERATURES IN THE UPPER 80S.

A GENERALLY FAIR AND MAINLY STABLE WEATHER PATTERN IS EXPECTED TO
PREVAIL FRIDAY THROUGH AT LEAST SUNDAY UNDER BUILDING RIDGE AND
NEAR NORMAL PRECIPITABLE WATER. AS A RESULT...EXPECT PARTLY CLOUDY
SKIES WITH A FEW PASSING SHOWERS ACROSS WINDWARD AREAS IN THE
MORNING....FOLLOWED BY SHOWERS AND SOME THUNDERSTORMS ACROSS
PORTIONS OF THE CORDILLERA CENTRAL AND WEST PUERTO RICO IN THE
AFTERNOON. UNDER EAST NORTHEAST WINDS...THE HEAVIEST SHOWERS AND
THUNDERSTORMS WILL BE FOCUSED OVER WEST AND SOUTHWEST PUERTO RICO
EACH AFTERNOON. AS RIDGE ALOFT FLATTENS NEXT WEEK AND A LOW
PRESSURE DEVELOPS ACROSS THE WESTERN CARIBBEAN...MOISTURE
ADVECTION IS THEN EXPECTED ACROSS THE LOCAL ISLANDS. THIS WILL
BRING A BETTER CHANCE OF SHOWER ACTIVITY WEDNESDAY THROUGH AT
LEAST FRIDAY.

&&

.AVIATION...VFR CONDS WILL PREVAIL AT MOST OF THE TAF SITES. BRIEF
MVFR CIGS POSSIBLE NEAR TJMZ/TJPS THRU 21Z. ENE WINDS OF 15-20 KT
EXPECTED THRU FRIDAY. NO SIG OPERATIONAL WX IMPACTS ATTM.

&&

.MARINE...WINDS OF 15-20 KT AND SEAS OF 4-6 FT CAN BE EXPECTED THROUGH
TONIGHT. AS A RESULT...SMALL CRAFT SHOULD EXERCISE CAUTION ACROSS
THE OFFSHORE WATERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 88 78 87 / 20 20 30 30
STT 79 89 79 89 / 20 20 30 30

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
538 AM AST FRI MAY 15 2015

.SYNOPSIS...AT UPPER LEVELS...A TROUGH WILL MOVE OUT OF THE AREATODAY
AND HIGH PRESSURE WILL APPROACH FROM THE WEST. BUT BEFORE IT CAN
GET OUT OF THE WESTERN CARIBBEAN A SECOND TROUGH FROM THE SAME LOW
WILL DIG INTO THE AREA WITH A JET STREAK THAT WILL BRUSH THE AREA
WITH 70 KNOTS WINDS. THE NEXT RIDGE WILL REACH THE AREA BY
THURSDAY AS STRONG HIGH PRESSURE BUILDS OVER THE SOUTHERN
CARIBBEAN.

AT MID LEVELS...LOW PRESSURE WILL KICK AROUND IN THE NORTHERN PART
OF THE WESTERN ATLANTIC FOR MUCH OF THE NEXT 10 DAYS WHILE HIGH
PRESSURE DOMINATES THE AREA FROM FLORIDA TO THE WINDWARD ISLANDS.
MID LEVELS ARE DRY TODAY AND THEN BECOME A LITTLE MORE MOIST
DURING THE UPCOMING WEEK.

AT LOWER LEVELS...A MODERATE SURFACE LOW WILL DRIFT AROUND IN THE
ATLANTIC WELL NORTH OF THE LEEWARD ISLANDS THROUGH MID WEEK NEXT
WEEK. AFTER WHICH HIGH PRESSURE WILL BE RESTORED TO THE LOCAL
AREA AND EAST SOUTHEAST TRADE WINDS WILL BECOME A LITTLE STRONGER.
MOISTURE AT LOWER LEVELS TENDS TO VARY...BUT IS EXPECTED TO
INCREASE THROUGH NEXT THURSDAY.

&&

.DISCUSSION...LIGHT TO MODERATE SHOWERS MOVED THROUGH THE
CARIBBEAN WATERS AND ACROSS SAINT CROIX AND EASTERN PUERTO
RICO...BECOMING WEAKER AS THEY MOVED INLAND. FLOW WAS STILL EAST
NORTHEAST BUT WILL TURN TO EAST SOUTHEAST LATER ON TODAY.
PRECIPITABLE WATER WILL INCREASE SLIGHTLY TODAY BUT WILL CONTINUE
TO INCREASE THROUGH MONDAY ACCORDING TO THE LATEST GFS SOLUTION.
AFTER A DIP ON TUESDAY...MOISTURE WILL PEAK AGAIN ON THURSDAY
AFTERNOON. AREAS OF UPPER LEVEL DIVERGENCE WILL PLAY VERY LITTLE
PART IN THE GROWTH OF ACTIVITY TODAY...BUT PATCHES OF DIVERGENCE
MIGRATE ACROSS THE AREA MORE LATER IN THE COMING WEEK. RAIN WILL
DEPEND MAINLY ON THE LOWER AND MID LEVEL MOISTURE. AND ALTHOUGH
LOW LEVEL MOISTURE WILL BE GOOD MOIST OF THE THE NEXT 10
DAYS...THE LAYER FROM 850 TO 550 MB IS STILL CONSISTENTLY DRYER
AND WILL LIMIT THE FORMATION OF SHOWERS. NEVERTHELESS EXPECT
THUNDERSTORMS...GENERALLY ISOLATED...EACH AFTERNOON IN THE WESTER
SECTIONS OF PUERTO RICO. ALTHOUGH SURFACE WINDS WILL BE SLIGHTLY
FROM THE EAST NORTHEAST...THE FLOW AT 850 MB WILL TURN MORE EAST
SOUTHEAST LATER THIS AFTERNOON AND SHOWERS SHOULD FORM FIRST IN
THE SOUTHWEST AND THEN STRENGTHEN IN THE WEST NORTHWEST OF PUERTO
RICO. WINDS IN THE LOWER LEVELS ARE EXPECTED TO KEEP THEIR WEAK
SOUTHERLY COMPONENT THROUGH THE END OF NEXT WEEK. THIS WILL LIMIT
RAINFALL IN THE NORTHEAST AND KEEP THE NORTH COAST WARMER THAN
NORMAL. NEXT WEEK.

&&

.AVIATION...MOSTLY VFR CONDS WILL PREVAIL ACROSS ALL TERMINALS THRU
THE FCST PERIOD. HOWEVER...PASSING SHOWERS OVER THE WATERS COULD
REACH PARTS OF THE WINDWARD AREAS OF THE ISLANDS THIS MORNING. BRIEF
MVFR CONDS AND MTN OBSCURATIONS POSSIBLE BETWEEN 15/18-22Z AS
SHRA/ISOLD TSRA IS EXPECTED ACROSS THE INTERIOR AND WESTERN
SECTIONS OF PR...IMPACTING MAINLY TJMZ...TJBQ AND IN THE VICINITY
OF TJPS. LOW LEVEL EAST TO NORTHEAST WINDS AT 5-15 KT EARLY...LIGHT
AND VRB DURING THE MORNING HRS OVER LAND...INCREASING AFTER 12Z
AT 15-20 KT WITH GUSTS IN THE MID 20S.

&&

.MARINE...SEAS REMAIN LESS THAN 6 FEET FOR THE MOST PART DURING
THE LAST PART OF THE WEEK AND WILL GENERALLY COME DOWN A LITTLE
BIT MORE BEFORE PEAKING OVERNIGHT ON SUNDAY. THE CARIBBEAN WILL
HAVE LOWER SEAS THAN THE ATLANTIC. SMALL CRAFT ADVISORIES ARE NOT
EXPECTED DURING THE NEXT 7 DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 86 77 / 20 30 20 30
STT 89 77 87 77 / 30 40 20 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
523 PM AST FRI MAY 15 2015

.SYNOPSIS...DEEP LAYER LOW WILL PERSIST OVER THE NORTH CENTRAL
ATLANTIC THROUGH NEXT WEEK...MAINTAINING A WESTERLY FLOW ALOFT
THROUGH THE FORECAST PERIOD. MID LEVEL DRY AIR BECOME SMALLER
OVER THE NEXT FEW DAYS AND DECREASE ON THURSDAY NEXT WEEK. AS A
RESULT...DEEPER MOISTURE IS FORECAST BY THE OPERATIONAL MODELS AS
AFOREMENTIONED UPPER TROUGH AMPLIFY NORTHEAST OF THE ISLANDS. AT
LOW LEVELS...WEAK HIGH PRESSURE WILL RELOCATE NORTH OF THE ISLANDS
BY EARLY NEXT WEEK.

&&

.DISCUSSION...SHOWERS AND THUNDERSTORMS DEVELOPED ACROSS THE CENTRAL
AND WESTERN PUERTO RICO. IN ADDITION...A STREAMER FORMED OVER TRUJILLO
ALTO...GUAYNABO AND BAYAMON LEAVING NEAR 0.5-1 INCHES IN SOME AREAS.
HOWEVER...RAINFALL ACCUMULATIONS RANGED BETWEEN 1-2 INCHES ACROSS
THE CENTRAL PUERTO RICO WITH A MAXIMUM OF 2.5 INCHES IN OROCOVIS
AND NE OF PONCE. MOSTLY SUNNY SKIES PREVAILED IN THE COASTAL AREAS
OF PUERTO RICO AND IN THE U.S. VIRGIN ISLANDS.

MOISTURE WILL INCREASE SLIGHTLY ACROSS THE REGION DURING THE WEEKEND.
AS A RESULT...EXPECT PARTLY CLOUDY SKIES WITH A FEW PASSING SHOWERS
ACROSS WINDWARD AREAS IN THE MORNING....FOLLOWED BY SHOWERS AND
SOME THUNDERSTORMS ACROSS PORTIONS OF THE CORDILLERA CENTRAL AND
WEST PUERTO RICO IN THE AFTERNOON. AS RIDGE ALOFT FLATTENS NEXT
WEEK AND LOW PRESSURES DEVELOP OVER THE WESTERN CARIBBEAN AND
CENTRAL ATLANTIC...MOISTURE WILL DEEPEN ACROSS THE ISLANDS. MODELS
ARE STARTING TO SHOW ABOVE NORMAL MOISTURE FOR THE SECOND PART OF
NEXT WEEK. THIS WILL LIKELY TO LEAD TO ENHANCED SHOWERS AND ISOLATED
EMBEDDED THUNDERSTORMS OVER THE USVI AND PORTIONS OF PUERTO RICO
ESPECIALLY ON THURSDAY. MODEL SOLUTION COULD CHANGE FROM RUN TO
RUN...THEREFORE WE WILL CONTINUE TO MONITOR THE MODEL SOLUTION
OVER THE NEXT SEVERAL DAYS TO SEE IF THE `WETTER` PATTERN
MATERIALIZE THE SECOND PART OF NEXT WEEK.

&&

.AVIATION...VFR CONDS EXPECTED TO PREVAIL ACROSS ALL TERMINALS THRU
THE FCST PERIOD WITH THE EXCEPTION OF TJMZ UNTIL 15/22Z WHERE SHRA
MAY BE OBSERVED...POSSIBLY CAUSING MVFR CONDS. BRIEF SHOWERS OVER
THE WATERS COULD REACH PARTS OF THE WINDWARD AREAS OF THE ISLANDS
THROUGH THE FORECAST PERIOD. LOW LEVEL EAST TO NORTHEAST WINDS AT 5-
15 KT EARLY...LIGHT AND VRB LATE TONIGHT INTO THE MORNING...INCREASING
AFTER 12Z TO AROUND 10-15 KT WITH GUSTS.

&&

.MARINE...SEAS OF 5 FEET OR LESS AND WINDS BELOW 18 KNOTS ARE
EXPECTED FOR THE NEXT FEW DAYS. NO SIGNIFICANT INCREASE IN WAVE
HEIGHT IS FORESEEN OVER THE NEXT 7 DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 77 88 76 88 / 30 20 30 30
STT 76 86 76 87 / 40 20 40 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
528 AM AST SAT MAY 16 2015

.SYNOPSIS...AT UPPER LEVELS...A STRONG TROUGH WELL NORTH NORTHEAST
OF THE AREA WILL CAUSE THE SUB TROPICAL JET TO INCREASE OVER THE
LOCAL AREA TODAY AND SUNDAY IN ANTI-CYCLONIC FLOW. ON MONDAY NIGHT
A TROUGH FROM THE LOW WILL EXTEND INTO AND CROSS THROUGH THE AREA.
THE RIDGE TO THE WEST WILL FOLLOW...CROSSING THROUGH ON THURSDAY
AND STALLING OVER THE AREA. CURRENTLY THE GFS HAS A SHORT WAVE
TROUGH MOVING THROUGH THE RIDGE ON THE FOLLOWING MONDAY.

AT MID LEVELS...HIGH PRESSURE IS THE DOMINANT FEATURE OVER THE
AREA. NEVERTHELESS THERE IS SOME MOISTURE AND INFLUENCE FROM A
SHEAR LINE THAT EXTENDS FROM THE NORTHEAST ACROSS THE AREA TODAY
AND WHOSE INFLUENCE CONTINUES THROUGH NEXT THURSDAY AT MID
LEVELS. THIS WILL INCREASE THE CHANCE OF SHOWERS OVER THE AREA.

AT LOWER LEVELS...MOISTURE FROM A SHEARLINE FROM A LOW TO THE
NORTHEAST WILL INCREASE UNSTEADILY THROUGH THURSDAY AFTERNOON WITH
THE DRIEST PERIOD OCCURRING MONDAY NIGHT WHEN MOST CONVECTION IS
USUALLY DEAD. THEREFORE EXPECT TO SEE SHOWERS AND THUNDERSTORMS
FORM OVER THE INTERIOR OF PUERTO RICO EACH DAY FOR THE NEXT 7
DAYS...AT LEAST...WITH SOME SPILLOVER TO THE COASTAL SECTIONS AS
WINDS SHIFT. DRIER AIR IS EXPECTED IN THE LOWER LEVELS NEXT
WEEKEND.

&&

.DISCUSSION...MOISTURE AND CONDITIONS MORE FAVORABLE TO CONVECTION
CONTINUE THEIR VERY GRADUAL RISE OVER THE AREA. SHOWERS HAVE BEEN
SEEN MOVING IN FROM THE EAST WITH MORE AREAL COVERAGE OVER THE
WATERS BETWEEN VIEQUES AND SAINT CROIX. MOST SHOWERS MOVING FROM
THE CARIBBEAN ARE MOVING ONSHORE IN PUERTO RICO THEN FADING. MOST
SHOWERS ARE VERY LIGHT WHEN CROSSING OVER THE U.S. VIRGIN ISLANDS.
THE GFS SHOWS A SUBSTANTIAL INCREASE IN THE PRECIPITABLE WATER AND
700 MB RELATIVE HUMIDITY IN A PATCH OF MOISTURE EXPECTED TO ENTER
THE AREA EARLY THIS AFTERNOON AROUND 16/18Z. THIS SHOULD PRIME
THE ISLAND FOR BETTER CONVECTION THAN SEEN THE LAST SEVERAL DAYS.
SLOWER WINDS WILL LEAD TO LONGER DURATION SHOWERS. THE HEAVIER
ONES WILL LIKELY PRODUCE URBAN AND SMALL STREAM FLOODING...MAINLY
IN THE INTERIOR PORTIONS OF THE ISLAND. WITH THE SHEAR LINE
HOLDING OVER THE AREA EXPECT SIMILAR CONDITION FOR THE NEXT
SEVERAL DAYS. AN INTRUSION OF DRIER AIR FROM A LARGE POOL OF DRY
AIR AT LOWER LEVELS OVER THE SUB TROPICAL ATLANTIC WILL CUT
THROUGH THE AREA IN A NARROW RIBBON ON MONDAY NIGHT ACCORDING TO
CURRENT SOLUTIONS...BUT MOISTURE WILL RETURN BEFORE THE HEATING
THE NEXT DAY TO FIRE OFF ANOTHER ROUND OF THUNDERSTORMS.

DRYING IS EXPECTED OVER NEXT WEEKEND WHEN THE PREVIOUSLY MENTIONED
DRY POOL MOVES IN OVER THE LOCAL AREA.

&&

.AVIATION...MOSTLY VFR CONDS WILL PREVAIL ACROSS ALL TERMINALS THRU
THE FCST PERIOD. HOWEVER...PASSING TRADE WIND SHOWERS OVER THE
WATERS COULD REACH PARTS OF THE WINDWARD AREAS OF THE ISLANDS IN THE
MORNING. BRIEF MVFR CONDS POSSIBLE BETWEEN 16/18-22Z AS SHRA/ISOLD
TSRA ARE EXPECTED ACROSS THE INTERIOR AND WESTERN SECTIONS OF
PR...IMPACTING MAINLY TJMZ AND THE VICINITY OF TJBQ/TJPS. MOUNTAIN
OBSCURATIONS WILL INCREASE DURING THE PERIOD. AFT 16/12Z...WINDS
EASTERLY AT 10 TO 15 KT WITH HIGHER GUSTS AND SEA BREEZE
VARIATIONS ARE EXPECTED TODAY.

&&

.MARINE...MARINE CONDITIONS REMAIN TRANQUIL WITH SEAS BETWEEN 2
TO 5 FEET. WINDS WILL CONTINUE BELOW 18 KNOTS ALTHOUGH HIGH GUSTS
ARE EXPECTED NEAR SHORE. WINDS INCREASE FRIDAY THROUGH SUNDAY OF
NEXT WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 76 88 77 / 40 40 40 30
STT 86 76 87 77 / 30 40 40 10

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
317 PM AST SAT MAY 16 2015

.SYNOPSIS...TROUGH PATTERN ACROSS NORTH CENTRAL ATLANTIC IS CAUSING
SUB-TROPICAL JET TO MODULATE OVER THE LOCAL ISLANDS. MID LEVEL DRY
AIR WILL GRADUALLY DECREASE OVER THE SEVERAL DAYS...RESULTING IN
BETTER CHANCE OF SHOWERS ACROSS THE LOCAL AREA...ESPECIALLY WESTERN
INTERIOR OF PR EACH AFTERNOON. AT LOW LEVELS...WEAK HIGH PRESSURE
WILL RELOCATE NORTH OF THE ISLANDS BY EARLY NEXT WEEK...PUSHING
ADDITIONAL TRADE WIND SHOWERS ACROSS THE WINDWARD SIDE OF THE ISLANDS.

&&

.DISCUSSION...SHOWERS WITH SOME HEAVY RAINFALL WERE OBSERVED ACROSS
PORTIONS OF WESTERN PUERTO RICO...SAN JUAN METROPOLITAN AREA AND ST.
THOMAS. ALSO A FEW THUNDERSTORMS DEVELOPED OVER ANASCO AND LAS
MARIAS. AVERAGE RAINFALL ACCUMULATIONS SO FAR THIS AFTERNOON HAVE
RANGED BETWEEN 1-2 INCHES ACROSS THE WEST PUERTO RICO WITH A MAXIMUM
OF 2-3 INCHES IN CAROLINA...ANASCO AND ST. THOMAS. VARIABLY TO
MOSTLY CLOUDY SKIES PREVAILED ELSEWHERE ACROSS THE ISLANDS MAINLY
DUE TO HIGH CLOUDS STREAMING WESTWARD OVER THE REGION.

MOISTURE WILL GRADUALLY INCREASE ACROSS THE REGION THROUGH THURSDAY.
IN ADDITION...AREAS OF DIFFLUENCE/DIVERGENCE ASSOCIATED WITH THE
SUB- TROPICAL JET ALOFT WILL GUARANTEE ACTIVE AFTERNOONS ACROSS
THE INTERIOR AND WEST PORTIONS OF PUERTO RICO. FOR THE WINDWARD
SIDE OF PR AND USVI...POCKETS OF MOISTURE EMBEDDED IN THE TRADES
WILL BRING BRIEF SHOWERS AT TIMES THROUGH THE NEXT SEVERAL DAYS.
MODELS ARE STARTING TO SHOW ABOVE NORMAL MOISTURE FOR THE SECOND
PART OF NEXT WEEK. THIS WILL LIKELY TO LEAD TO ENHANCED SHOWERS
AND ISOLATED EMBEDDED THUNDERSTORMS OVER THE USVI AND PORTIONS OF
PUERTO RICO ESPECIALLY ON THURSDAY. MODEL SOLUTIONS COULD VARY
FROM RUN TO RUN...THEREFORE WE WILL CONTINUE TO MONITOR THE MODEL
SOLUTION OVER THE NEXT SEVERAL DAYS TO SEE IF THE `WETTER` PATTERN
MATERIALIZE THURSDAY AND FRIDAY.

&&

.AVIATION...VFR CONDS EXPECTED TO PREVAIL ACROSS ALL TERMINALS THRU
THE FCST PERIOD WITH THE EXCEPTION OF TJMZ WHERE MVFR CONDS ARE
POSSIBLE THRU 22Z. BRIEF SHOWERS OVER THE WATERS COULD REACH PARTS
OF THE WINDWARD AREAS OF THE ISLANDS THROUGH THE FORECAST PERIOD.

&&

.MARINE...TRANQUIL MARINE CONDS ARE EXPECTED OVER THE NEXT SEVERAL
DAYS WITH SEAS OF 4 FEET OR LESS AND WINDS BELOW 18 KNOTS. NO
SIGNIFICANT INCREASE IN WAVE HEIGHT IS FORESEEN OVER THE NEXT 7
DAYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 87 77 88 / 40 40 30 30
STT 76 87 76 87 / 40 40 10 20

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
602 AM AST SUN MAY 17 2015

.SYNOPSIS...AT UPPER LEVELS...A BRANCH OF THE SUB TROPICAL JET
CONTINUES OVER THE LOCAL AREA WITH WEST SOUTHWEST WINDS UP TO
AROUND 60 KNOTS THROUGH TUESDAY NIGHT. A TROUGH ALSO PASSES
NORTHEAST OF THE AREA ON TUESDAY FOLLOWED BY A MILD RIDGE ON
WEDNESDAY. RIDGING THEN CONTINUES EAST OF THE AREA INTO THE
WEEKEND WITH A NEW RIDGE REINFORCING IT NEXT SUNDAY.

AT MID LEVELS...A DOUBLE LOBED LOW ROTATES AROUND IN THE WEST
CENTRAL ATLANTIC UNTIL WEDNESDAY CAUSING SLIGHTLY LOWER PRESSURES
OVER THE AREA. THEN IT LIFTS AWAY FROM THE AREA. HIGH PRESSURE
THEN DOMINATES THE AREA THROUGH THE MIDDLE OF NEXT WEEK. THE
ATMOSPHERE FROM 850-550 MB REMAINS RELATIVELY DRY NEXT WEEK.

AT LOWER LEVELS...A SHEAR LINE FROM THE LOW TO THE NORTH NORTHEAST
WILL CONTINUE TO AFFECT THE LOCAL AREA FOR SEVERAL MORE
DAYS...CONCENTRATING MOISTURE AND SHOWERS OVER THE AREA. A RIBBON
OF DRIER AIR CROSSES THROUGH FROM THE SOUTHEAST ON MONDAY NIGHT
FOLLOWED BY ANOTHER BROAD PATCH OF MOISTURE. DRIER AIR ATTEMPTS TO
MOVE IN OVER THE WEEKEND BUT SEVERAL PATCHES OF MOISTURE ARE NOW
SHOWN MOVING THROUGH.

&&

.DISCUSSION...SHOWERS INCREASED OVERNIGHT AND NOW PEPPER THE LOCAL
WATERS AROUND THE NORTH AND SOUTH SIDES OF THE ISLANDS. A FEW
SHOWERS HAVE ALSO MOVED INLAND ON THE EASTERN SIDE OF PUERTO RICO
AND SHOWERS HAVE ALSO CROSSED THE U.S. VIRGIN ISLANDS. SINCE THE
SHOWERS ARE SMALL AND GENERALLY LIGHT TO MODERATE...ACCUMULATIONS
HAVE GENERALLY BEEN SLIGHT. THE GFS SHOWS MOISTURE ASSOCIATED WITH
THE SHEAR LINE OVER AND JUST NORTH OF PUERTO RICO AND THE U.S.
VIRGIN ISLANDS...BUT IT IS NOT AS STRONG AS YESTERDAY AND WILL
FADE SLIGHTLY DURING THE DAY. NEVERTHELESS THIS WILL SERVE TO
MAINTAIN FAVORABLE CONDITIONS FOR INSTABILITY AND SHOWERS...AND A
FEW THUNDERSTORMS. THE THUNDERSTORMS WILL MAINLY BE IN WESTERN
PUERTO RICO. SOME URBAN AND SMALL STREAM FLOODING WILL BE POSSIBLE
AGAIN TODAY...ALTHOUGH AGAIN NOT QUITE AS MUCH AS SATURDAY. THE
SHEAR LINE PULLS AWAY SLOWLY MONDAY AND TUESDAY THEN A BULGE OF
MOISTURE FROM THE ITCZ AND LOW PRESSURE NORTH OF PANAMA AT 700 MB
WILL CROSS THE AREA ON THURSDAY AFTERNOON BRINGING ANOTHER WAVE OF
SHOWERS AHEAD OF DRIER LOW LEVEL AIR TO THE SOUTHEAST. ANOTHER
WEAK TROUGH WILL BRING MORE MOISTURE ON SATURDAY LEAVING THE
DRIEST AIR IN THE WESTERN TROPICAL ATLANTIC EAST OF THE WINDWARD
ISLANDS.

THIS REPRESENTS AND OVERALL MOISTENING OF THE PATTERN THAT HAD
BEEN IN PLACE UP TO THIS PAST WEEK...AND WHILE IT MAY NOT BE
SUFFICIENT TO BRING RAINFALL LEVELS UP TO NORMAL VALUES FOR THE
MONTH...IT WILL HELP ALLEVIATE SOME OF THE DEFICIT BEING
EXPERIENCED.

&&

.AVIATION...MOSTLY VFR CONDS WILL PREVAIL ACROSS ALL TERMINALS THRU
THE FCST PERIOD. DURING THE MORNING HOURS BRIEF SHOWERS OVER THE
WATERS COULD REACH PARTS OF THE WINDWARD AREAS OF THE ISLANDS. BRIEF
MVFR CONDS POSSIBLE BETWEEN 17/18-22Z AS SHRA/ISOLD TSRA ARE
EXPECTED ACROSS THE INTERIOR AND WESTERN SECTIONS OF PR...IMPACTING
MAINLY TJMZ AND THE VICINITY OF TJBQ/TJPS. CALM TO LIGHT AND
VARIABLE WINDS NEAR THE SFC...AFT 17/12Z E-NE WINDS BETWEEN 10 AND
15 KTS AND LOCALLY HIGHER IN/NEAR SHRA/TSRA.


&&

.MARINE...WINDS AND SEAS ARE QUIETER TODAY WITH SOME BUOYS
REPORTING LESS THAN 3 FEET AND MOST BUOYS REPORTING LESS THAN 4
FEET. WINDS WILL INCREASE SOME NOW THROUGH MONDAY...BUT THE
PRESSURE GRADIENT WEAKENS EARLY THIS WEEK AND WINDS WILL SUBSIDE
EVEN MORE THAN PREVIOUSLY. NO SMALL CRAFT ADVISORIES ARE
ANTICIPATED THROUGH THE TUESDAY AFTER NEXT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 76 88 77 / 40 30 30 20
STT 87 75 87 76 / 40 10 10 10

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
303 PM AST SUN MAY 17 2015

.DISCUSSION...DECENT MOISTURE REMAINS TODAY (1.63 IN. ON 12Z TJSJ
SOUNDING) PLUS AN OVERHEAD UPPER JET...SO PRETTY GOOD SHOWERS AND
A FEW THUNDERSTORMS HAVE DEVELOPED FOR MUCH OF PR ESPECIALLY IN THE
WEST. SCATTERED SHOWERS AGAIN TONIGHT EVERYWHERE EXCEPT WEST PR.
DRIER AIR IS APPROACHING FROM EAST BUT SHOULD BE ONLY A SLIGHT
DROP OFF BY MON AFTERNOON. THE JET WILL STICK AROUND ON MON TOO
FOR ANOTHER ROUND OF CONVECTION SIMILAR TO TODAY.

MORE MOISTURE WILL BE MOVING NORTHWEST IN EASTERN CARIBBEAN BY
WED-THU FOR ANOTHER GOOD CHANCE OF SHOWERS MAINLY THU. BUT THE
HIGHEST PRECIPITABLE WATER AMOUNTS WILL HEAD INTO THE WESTERN
CARIBBEAN. GFS KEEPS MOISTURE FAIRLY CLOSE TO SEASONAL LEVELS INTO
NEXT WEEKEND...EXCEPT DRY ON TUE. AM CAUTIOUSLY OPTIMISTIC FOR
BETTER RAINFALL CHANCES MOST OF THIS WEEK.

&&

.AVIATION...MOSTLY VFR CONDS EXPECTED ACROSS ALL THE TAF SITES
EXCEPT TJMZ WHERE AFTERNOON CONVECTION COULD GENERATE MVFR CONDS
THRU 17/22Z. VCSH POSSIBLE TONIGHT ACROSS LEEWARD AND USVI TERMINAL.
EAST WINDS AROUND 15 KT WILL PREVAIL BELOW FL050...EXCEPT NEAR SHRA
WHERE HIGHER GUSTS ARE POSSIBLE AT TIMES.

&&

.MARINE...WINDS/SEAS AT BUOY 41043 CLIMBED BRIEFLY THIS MORNING TO
20 KT/7 FT BUT HAS BACKED OFF A LITTLE SINCE. THINK THERE ARE SOME
WIND WAVES TO 5 FT IN OUR NORTHWEST WATERS AND SHOULD CONTINUE
INTO MON. NO SIGNIFICANT SWELLS ARE APPROACHING AND DO NOT EXPECT
WINDS ENOUGH TO CAUSE SEAS HIGHER THAN 5 FT THIS WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 89 77 89 / 30 30 20 20
STT 76 87 77 87 / 10 10 10 20

[cycloneye]

This occurred on Sunday afternoon in Southern Puerto Rico as it tried to go down but remained up.

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
301 PM AST MON MAY 18 2015

.SYNOPSIS...BROAD POLAR TROUGH NORTH OF THE REGION AND ANTICYCLONIC
FLOW ALOFT AND SPREAD ACROSS THE EASTERN CARIBBEAN... WILL MAINTAIN
PREVAILING WESTERLIES ACROSS THE FORECAST AREA THROUGH TUESDAY.
MEANWHILE...A MID LEVEL SHORT WAVE TROUGH WILL CONTINUE TO ROUND
THE BASE OF THE UPPER TROUGH AND MOVE EASTWARDS ACROSS THE REGION
THROUGH TUESDAY. SURFACE HIGH PRESSURE RIDGE EXTENDS ACROSS THE
SOUTHWEST ATLANTIC...WHILE A FRONTAL SHEAR LINE AND AN INDUCED LOW
LEVEL TROUGH IS STALLED JUST NORTH OF THE REGION. THIS FEATURE WILL
SLOWLY DISSIPATE AND WEAKEN DURING THE NEXT DAY OR SO. THE OVERALL
PATTERN IS HELPING TO CREATE WEAK LOW LEVEL CONVERGENCE AND A LIGHT
TO MODERATE EAST TO NORTHEAST LOW LEVEL WIND FLOW ACROSS THE FORECAST
AREA.

&&

.DISCUSSION...LOCAL SEA BREEZE CONVERGENCE ALONG WITH PROXIMITY OF UPPER
LEVEL DISTURBANCE MOVING ACROSS THE REGION TODAY...WAS SUFFICIENT
TO SUPPORT AFTERNOON CONVECTION ACROSS PARTS OF THE ISLAND TODAY.
HOWEVER...MOST OF THE ACTIVITY WAS FOCUSED OVER THE INTERIOR AND
WEST SECTIONS OF PUERTO RICO...WHERE THE HEAVIER SHOWERS AND ISOLATED
THUNDERSTORMS WERE DETECTED BY THE NATIONAL WEATHER SERVICE DOPPLER
WEATHER RADAR. SOME OF THE SHOWERS WERE MODERATE TO LOCALLY HEAVY
AT TIMES BUT WERE MAINLY IN ISOLATED SPOTS.

THE TJSJ 18/12Z UPPER AIR SOUNDING AS WELL AS SATELLITE DERIVED
PRECIPITABLE WATER SUGGESTED LAYERED PWAT VALUES OF AROUND 1.60
INCHES. THIS WAS MORE THAN ENOUGH TO ALLOW FOR PERIODS OF THE
DIURNAL CONVECTION ALTHOUGH SO FAR THE ACTIVITY HAD NOT BEEN
WIDESPREAD. MOST OF THE SHOWER ACTIVITY OVER LAND WILL DIMINISH
JUST AFTER SUNSET LEAVING PARTLY CLOUDY SKIES. EARLY MORNING
PASSING SHOWERS WILL AGAIN REACH PORTIONS OF THE EAST COASTAL
SECTIONS OF THE ISLANDS AS LATEST MODEL GUIDANCE CONTINUE TO
SUGGEST OCCASIONAL SURGES OF LOW LEVEL MOISTURE ADVECTION ACROSS
THE NORTHEASTERN CARIBBEAN OVER THE NEXT FEW DAYS.

STILL LOOKING FOR AN INCREASING TROPICAL MOISTURE TREND BY
WEDNESDAY AND THURSDAY AS AN EASTERLY PERTUBATION WILL MOVE
ACROSS THE AREA. RECENT MODEL GUIDANCE CONTINUED TO SUGGEST
INCREASING PERCEPTIBLE WATER VALUES TO INCREASE TO NEAR 2.00
INCHES BY THE LATTER PART OF THE WEEK. THIS ALONG WITH LOCAL SEA
BREEZE CONVERGENCE AND GOOD VENTILATION ALOFT WILL SUPPORT INCREASE
POTENTIAL AND BETTER CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORM
DEVELOPMENT AT LEAST THROUGH THURSDAY AND POSSIBLY INTO FRIDAY.

&&

.AVIATION...SHRA/TSRA EXPECTED FOR THE REST OF THE AFTERNOON ACROSS
CENTRAL AND WESTERN PR. THIS ACTIVITY WILL AFFECT AREAS IN AND
AROUND TJMZ...TJBQ...AND TJPS...CAUSING VCSH/VCTS AT THOSE TERMINALS
AND LIKELY AFFECTING TJMZ DIRECTLY WITH MVFR CONDS BETWEEN 18/18Z TO
18/22Z. MTN OBSCURATIONS ARE TO BE EXPECTED WITH THIS ACTIVITY.
CONDS EXPECTED TO IMPROVE AFTER 18/23Z WITH PASSING SHRA REMAINING
ACROSS THE LOCAL AREA...CAUSING BRIEF VCSH ACROSS MOST OF THE LOCAL
TERMINALS. EASTERLY WINDS WITH SEA BREEZE VARIATIONS UNTIL
18/23Z...BECOMING LIGHT AND VARIABLE OVERNIGHT.

&&

.MARINE...SEAS ARE EXPECTED TO REMAIN AT 5 FEET OR LESS AND GENTLE
TO MODERATE EASTERLY TRADE WINDS OF 15 KTS OR LESS THROUGH THE MIDDLE
OF THE WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 76 89 77 88 / 30 30 30 30
STT 74 86 74 87 / 30 30 30 30

[cycloneye]

Here is a great site that includes composite radars from the Caribbean and has a good model section.



http://www.barbadosweather.org/BMS_radar_Composite.php

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
632 AM AST TUE MAY 19 2015

.SYNOPSIS...
AN UPPER LEVEL RIDGE WILL MOVE FROM THE WEST ACROSS THE REGION
TODAY. THE WESTERLY FLOW WILL CONTINUE TO PREVAIL ALOFT ACROSS
THE CARIBBEAN SEA DURING THE NEXT FEW DAYS. MEANWHILE...A MID
LEVEL SHORT WAVE TROUGH WILL CONTINUE TO BE THE DOMINANT WEATHER
FEATURE AT THAT LEVEL AT LEAST UNTIL THE WEEKEND. A SURFACE HIGH
PRESSURE AND A WEAKENING SHEAR LINE WILL PRODUCE SURFACE
CONVERGENCE TO MAINTAIN AN EASTERLY TRADE WIND FLOW ACROSS THE
REGION.

&&

.DISCUSSION...
THE NATIONAL WEATHER SERVICE DOPPLER RADAR DETECTED SHOWERS MAINLY
ACROSS THE LOCAL WATERS AND SOME OF THEM MOVED ALONG THE NORTHERN
COAST OF PUERTO RICO AND THE ISLAND OF ST CROIX OVERNIGHT. TRADE
WIND SHOWERS ARE ONCE AGAIN EXPECTED ACROSS THE WINDWARD SECTIONS
OF NORTHERN AND EASTERN PUERTO RICO AS WELL AS ACROSS THE U.S.
VIRGIN ISLANDS FROM TIME TO TIME DURING THE MORNING HOURS.
HOWEVER...A DRYER AIR MASS IS EXPECTED TO CONTINUE OVER THE
REGION THIS MORNING. FOR THE AFTERNOON...THE AVAILABLE MOISTURE
WILL COMBINE WITH THE LOCAL EFFECTS AND DIURNAL HEATING TO
PRODUCE ANOTHER ROUND OF SHOWERS AND THUNDERSTORM ACROSS THE
INTERIOR AND WESTERN SECTIONS OF PUERTO RICO. IN ADDITION...
AFTERNOON CONVECTION CAN BE EXPECTED ACROSS PORTIONS OF EASTERN
PUERTO RICO AND THE U.S. VIRGIN ISLANDS.

ALTHOUGH THE DYNAMICS ACROSS THE REGION ARE NOT THE MOST
FAVORABLE...LATEST MODEL GUIDANCE CONTINUES TO SUGGEST AN
INCREASE OF TROPICAL MOISTURE ADVECTION ACROSS THE CWA OVER THE
NEXT FEW DAYS. THEREFORE...THERE IS A BETTER CHANCE OF SHOWERS
AND THUNDERSTORM DEVELOPMENT WEDNESDAY THROUGH FRIDAY. OVERNIGHT
AND EARLY MORNING PASSING SHOWERS ACROSS THE WINDWARD SECTIONS OF
PR AND THE USVI...FOLLOWED BY AFTERNOON CONVECTION WITH ISOLD
T-STORMS ACROSS PORTIONS OF THE INTERIOR AND WESTERN PR ARE
EXPECTED EACH DAY FOR THE REST OF THE WEEK.

&&

.AVIATION...
MAINLY VFR CONDS WILL CONTINUE ACROSS ALL TERMINALS THRU THE FCST
PERIOD EXCEPT AREAS OF MVFR CIGS IN SHRA PSBL IN AND ARND
TNCM/TKPK. BETWEEN 19/17-22Z SHRA/TSRA ARE EXPECTED OVER
WESTERN/CENTRAL PR WITH MVFR CONDS MTN OBSCURATIONS. LIGHT AND
VARIABLE WINDS OVERNIGHT...AFT 19/12Z EXPECT LOW LEVEL EASTERLIES
UP TO FL095 AROUND 10-14 KT...WITH SEA BREEZE VARIATIONS NR SFC
AFT 19/14Z. WNDS ABV FL110 WLY INCRG TO 65 KT BY FL450.

&&

.MARINE...TRANQUIL MARINE CONDITIONS ARE EXPECTED OVER THE NEXT
FEW DAYS WITH SEAS BELOW 5 FEET AND WINDS AROUND 15 KNOTS. WINDS
CAN BE LOCALLY HIGHER IN AND AROUND SHOWER ACTIVITY.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 87 77 89 76 / 30 20 20 20
STT 86 76 87 75 / 30 40 40 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
323 PM AST TUE MAY 19 2015

.SYNOPSIS...BROAD MID TO UPPER LEVEL TROUGH SLOWLY SHIFTING EAST
ACROSS THE WESTERN ATLANTIC...WITH UPPER RIDGE ANCHORED ACROSS THE
EASTERN CARIBBEAN. THIS WILL MAINTAIN THE UPPER LEVEL WESTERLIES
AND OVERALL SUBSIDENT ALOFT AS RIDGE IS TO BUILD ACROSS THE REGION
OVER THE NEXT FEW DAYS. SURFACE HIGH PRESSURE RIDGE ACROSS THE SOUTHWEST
ATLANTIC...AND A WEAK LOW LEVEL TROUGH NOW SHIFTING WESTWARD ACROSS
THE NORTHEASTERN CARIBBEAN...WILL MAINTAIN PREVAILING EASTERLIES ACROSS
THE FORECAST AREA THROUGH THE END OF THE WEEK. SATELLITE IMAGERY SHOWED
AN AREA OF MOISTURE ACCOMPANYING THE WEAK EASTERLY PERTURBATION/TROUGH
NOW ENTERING THE EASTERN CARIBBEAN....WITH A SLOT OF DRIER AIR
PRESENTLY MOVING ACROSS THE LOCAL ISLANDS AND REGIONAL WATERS.

&&

.DISCUSSION...MOSTLY SUNNY AND OVERALL DRY CONDITIONS WERE NOTED
DURING THE MORNING HOURS. BY AFTERNOON SEA BREEZE CONVERGENCE AND
LOCAL EFFECTS AIDED IN THE DEVELOPMENT OF SOME CLOUDS ACROSS PARTS
OF THE INTERIOR SECTIONS OF PUERTO RICO...AND OVER SOME OF THE
U.S. VIRGIN ISLANDS WHERE A FEW SHOWERS FORMED AND QUICKLY STREAMED
WESTWARDS. EXPECT A GRADUAL CLEARING AND DIMINISHING PRECIPITATION
OVER LAND BY SUNSET AND DURING MOST OF THE OVERNIGHT HOURS.

HOWEVER...MOISTURE ACCOMPANYING A WEAK EASTERLY PERTURBATION WILL
BRING SHOWERS TO THE COASTAL AREAS OF THE ISLANDS DURING THE EARLY
MORNING HOURS. ON WEDNESDAY...AND FOR THE REST FOR THE WORK WEEK
MODELS STILL SUGGEST AN INCREASE IN LAYERED PRECIPITABLE WATERS
AND TROPICAL MOISTURE ACROSS THE FORECAST AREA. THIS INCREASE
ALONG WITH LOCAL AND DIURNAL EFFECTS WILL INCREASE THE CHANCE FOR
ADDITIONAL SHOWERS AND THUNDERSTORM ACTIVITY ACROSS THE ISLANDS
AND SURROUNDING WATERS. IMPROVING WEATHER CONDITION AND DRIER
CONDITIONS EXPECTED BY THE UPCOMING WEEKEND.

&&

.AVIATION...VFR CONDS WILL CONTINUE ACROSS ALL TERMINALS THRU THE
FCST PERIOD. BETWEEN 19-22Z SHRA ARE EXPECTED OVER WESTERN/CENTRAL
PR WITH POSSIBLE MVFR CONDS AND MTN OBSCURATIONS. EASTERLY WINDS AT
AROUND 10 KNOTS WITH SEA BREEZE VARIATIONS THIS AFTERNOON...THEN
LIGHT AND VARIABLE WINDS EXPECTED OVERNIGHT. BRIEF SHRA EXPECTED
OVERNIGHT ACROSS THE AREA MAY CAUSE VCSH ACROSS
TNCM/TKPK/TIST/TISX/TJSJ.

&&

.MARINE...SEAS CONTINUE TO SUBSIDE TO 5 FEET OR LESS AND WINDS
AROUND 10 TO 15 KNOTS. FAIRLY TRANQUIL SEAS AND GENTLE TO MODERATE
EASTERLY TRADES...FOR THE NEXT FEW DAYS WITH NO SIGNIFICANT HAZARDS
AT THIS TIME.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 78 89 77 89 / 20 20 20 40
STT 77 87 77 87 / 40 40 40 40

[cycloneye]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
514 AM AST WED MAY 20 2015

.DISCUSSION...MOISTURE TO SLOWLY INCREASE OVER LOCAL ISLANDS
THROUGH THU WITH PRECIPITABLE WATER APPROACHING 2 INCHES. 00Z
TJSJ SOUNDING AND MIMIC-TPW PRODUCT SUGGEST IT MIGHT BE CLOSER
TO 2 INCHES THAN GFS IMPLIES. ONLY A VERY WEAK LOW LEVEL WAVE IS
APPROACHING IN THE EASTERN CARIBBEAN AND NOT LIKELY TO CONTRIBUTE
TO DEVELOPING SHOWERS BY ITSELF. BUT A BROAD UPPER LEVEL JET IS
OVER THE AREA TOO AND UPPER DIVERGENCE COULD HELP SUSTAIN
CONVECTION ONCE IT STARTS...MORE LIKELY ON THU AS GFS SHOWS UPPER
DIVERGENCE OVER THE AREA THEN FROM 18Z-24Z. CIRRUS CLOUDS DO NOT
APPEAR WIDESPREAD OR THICK ENOUGH TO LIMIT DAYTIME HEATING SO
EXPECT WESTERN PR ESPECIALLY TO RECEIVE GOOD RAINS. THUNDER TOO
ESPECIALLY THU.

FRI TO BEGIN A SLOW DRYING TREND AGAIN AS THE WAVE MOVES ON BUT
DOES NOT BECOME VERY DRY AGAIN UNTIL EARLY NEXT WEEK WHEN A MID
LEVEL RIDGE BUILDS OVER FL AND BAHAMAS. GFS SHOWS IT NOT CAUSING
SIGNIFICANT MID-LEVEL DRYING THOUGH UNTIL ABOUT WED.

&&

.AVIATION...VFR CONDS WILL CONTINUE ACROSS MOST OF THE TERMINALS
THRU THE FORECAST PERIOD. HOWEVER...AFTERNOON CONVECTION OVER THE
INTERIOR AND WESTERN PR COULD PRODUCE BRIEF MVFR/IFR CONDS IN AND
AROUND TJBQ AND TJMZ BETWEEN 20/19-22Z. MOUNTAIN OBSCURATIONS ARE
ALSO LIKELY ACROSS CENTRAL AND WEST INTERIOR OF PR. WINDS WILL VEER
TO ESE THROUGHOUT THE DAY...RANGING BETWEEN 10-15 KTS BELOW FL070.

&&

.MARINE...WINDS TO BE 15 KNOTS OR LESS TODAY AND WILL GRADUALLY
INCREASE TOWARDS THE WEEKEND. BUT SEAS TO BE GENERALLY 4 FT OR
LESS UNTIL TRADE WINDS INCREASE AGAIN...REACHING 5 FT PROBABLY FRI
NIGHT/SAT.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU 88 77 90 77 / 30 20 40 40
STT 86 77 87 79 / 40 40 40 40